Inbred corn line PHW20

ABSTRACT

According to the invention, there is provided an inbred corn line, designated PHW20. This invention thus relates to the plants and seeds of inbred corn line PHW20 and to methods for producing a corn plant produced by crossing the inbred line PHW20 with itself or with another corn plant. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHW20 with another corn line or plant and to crosses with related species.

FIELD OF THE INVENTION

This invention is in the field of corn breeding, specifically relatingto an inbred corn line designated PHW20.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety/hybridvarious desirable traits. For field crops, these traits may includeresistance to diseases and insects, tolerance to heat and drought,reducing the time to crop maturity, greater yield, and better agronomicquality. With mechanical harvesting of many crops, uniformity of plantcharacteristics such as germination and stand establishment, growthrate, maturity, and fruit size, is important.

Field crops are bred through techniques that take advantage of theplant's method of pollination. A plant is self-pollinated if pollen fromone flower is transferred to the same or another flower of the sameplant. A plant is cross-pollinated if the pollen comes from a flower ona different plant.

Plants that have been self-pollinated and selected for type for manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny. A cross between twohomozygous lines produce a uniform population of hybrid plants that maybe heterozygous for many gene loci. A cross of two plants eachheterozygous at a number of gene loci will produce a population ofhybrid plants that differ genetically and will not be uniform.

Corn plants (Zea mays L.) can be bred by both self-pollination andcross-pollination techniques. Corn has separate male and female flowerson the same plant, located on the tassel and the ear, respectively.Natural pollination occurs in corn when wind blows pollen from thetassels to the silks that protrude from the tops of the incipient ears.

The development of corn hybrids requires the development of homozygousinbred lines, the crossing of these lines, and the evaluation of thecrosses. Pedigree breeding and recurrent selection breeding methods areused to develop inbred lines from breeding populations. Breedingprograms combine the genetic backgrounds from two or more inbred linesor various other broad-based sources into breeding pools from which newinbred lines are developed by selfing and selection of desiredphenotypes. The new inbreds are crossed with other inbred lines and thehybrids from these crosses are evaluated to determine which of thosehave commercial potential.

Pedigree breeding for single-gene traits starts with the crossing of twogenotypes, each of which may have one or more desirable characteristicsthat is lacking in the other or which complement the other. If the twooriginal parents do not provide all of the desired characteristics,other sources can be included in the breeding population. In thepedigree method, superior plants are selfed and selected in successivegenerations. In the succeeding generations the heterozygous conditiongives way to homogeneous lines as a result of self-pollination andselection. Typically in the pedigree method of breeding five or moregenerations of selfing and selection is practiced: F₁ →F₂ ; F₂ →F₃ ; F₃→F₄ ; F₄ →F₅, etc.

Backcrossing can be used to improve an inbred line. Backcrossingtransfers a specific desirable trait from one inbred or source to aninbred that lacks that trait This can be accomplished for example byfirst crossing a superior inbred (A) (recurrent parent) to a donorinbred (non-recurrent parent), which carries the appropriate gene(s) forthe trait in question. The progeny of this cross is then mated back tothe superior recurrent parent (A) followed by selection in the resultantprogeny for the desired trait to be transferred from the non-recurrentparent. After five or more backcross generations with selection for thedesired trait, the progeny will be heterozygous for loci controlling thecharacteristic being transferred, but will be like the superior parentfor most or almost all other genes. The last backcross generation wouldbe selfed to give pure breeding progeny for the gene(s) beingtransferred.

A single cross hybrid corn variety is the cross of two inbred lines,each of which has a genotype which complements the genotype of theother. The hybrid progeny of the first generation is designated F₁. Inthe development of hybrids only the F₁ hybrid plants are sought.Preferred F₁ hybrids are more vigorous than their inbred parents. Thishybrid vigor, or heterosis, can be manifested in many polygenic traits,including increased vegetative growth and increased yield.

The development of a hybrid corn variety involves three steps: (1) theselection of plants from various germplasm pools; (2) the selfing of theselected plants for several generations to produce a series of inbredlines, which, although different from each other, each breed true andare highly uniform; and (3) crossing the selected inbred lines withunrelated inbred lines to produce the hybrid progeny (F₁). During theinbreeding process in corn, the vigor of the lines decreases. Vigor isrestored when two unrelated inbred lines are crossed to produce thehybrid progeny (F₁). An important consequence of the homozygosity andhomogeneity of the inbred lines is that the hybrid between any twoinbreds will always be the same. Once the inbreds that give a superiorhybrid have been identified, the hybrid seed can be reproducedindefinitely as long as the homogeneity of the inbred parents ismaintained.

A single cross hybrid is produced when two inbred lines are crossed toproduce the F₁ progeny. A double cross hybrid is produced from fourinbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybridsare crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F₁hybrids is lost in the next generation (F₂). Consequently, seed fromhybrid varieties is not used for planting stock.

Corn is an important and valuable field crop. Thus, a continuing goal ofplant breeders is to develop high-yielding corn hybrids that areagronomically sound based on stable inbred lines. The reasons for thisgoal are obvious: to maximize the amount of grain produced with theinputs used and minimize susceptibility to environmental stresses. Toaccomplish this goal, the corn breeder must select and develop superiorinbred parental lines for producing hybrids. This requiresidentification and selection of genetically unique individuals which ina segregating population occur as the result of a combination ofcrossover events plus the independent assortment of specificcombinations of alleles at many gene loci which results in specificgenotypes. Based on the number of segregating genes, the frequency ofoccurrence of an individual with a specific genotype is less than 1 in10,000. Thus, even if the entire genotype of the parents has beencharacterized and the desired genotype is known, only a few if anyindividuals having the desired genotype may be found in a large F₂ or S₀population from the cross. Typically, however, the genotype of neitherthe parents nor the desired genotype is known in any detail.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred corn line,designated PHW20. This invention thus relates to the seeds of inbredcorn line PHW20, to the plants of inbred corn line PHW20, and to methodsfor producing a corn plant produced by crossing the inbred line PHW20with itself or another corn line. This invention further relates tohybrid corn seeds and plants produced by crossing the inbred line PHW20with another corn line or a

DEFINITIONS

In the description and examples that follow, a number of terms are usedherein. In order to provide a clear and consistent understanding of thespecification and claims, including the scope to be given such terms,the following definitions are provided:

BAR PLT=BARREN PLANTS. This is the number of plants per plot that werenot barren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near thetime of pollination, and is an indication of whether a hybrid or inbredwould snap or break near the time of flowering under severe winds. Dataare presented as percentage of plants that did not snap.

BU ACR=YIELD (BUSHELS/ACRE). Actual yield of the grain at harvestadjusted to 15.5% moisture. ABS is in absolute terms and % MN is percentof the mean for the experiments in which the inbred or hybrid was grown.

CLD TST=COLD TEST. This is the percentage of kernels that germinateunder cold soil conditions. ABS =absolute measurement and % MN ispercentage of mean of the experiments in which inbred or hybrid wasgrown.

COB SC=COB SCORE. The cob score is a rating of how well the grain isshelled off the cob and how badly the cob is broken up going through thecombine. This is given as a 1 to 9 score with 9 being very good. A highscore indicates that the grain shells off of the cob well, and the cobdoes not break.

DRP EAR=DROPPED EARS. This is a measure of the number of dropped earsper plot and represents the percentage of plants that did not drop earsprior to harvest.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to thetop developed ear node attachment and is measured in inches.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher therating the larger the ear size.

EST CNT=EARLY STAND COUNT. This is a measure of the stand establishmentin the spring and represents the number of plants that emerge on a perplot basis for the inbred or hybrid.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heatunits required for an inbred line or hybrid to have approximately 50percent of the plants shedding pollen and is measured from the time ofplanting. Growing degree units are calculated by the Barger Method,where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimumtemperature used is 50° F. For each inbred or hybrid it takes a certainnumber of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for aninbred line or hybrid to have approximately 50 percent of the plantswith silk emergence from time of planting. Growing degree units arecalculated by the Barger Method as given in GDU SHD definition.

GRN QUL=GRAIN QUALITY. This is a 1 to 9 rating for the general qualityof the shelled grain as it is harvested based on such factors as thecolor of the harvested grain, any mold on the grain, and any crackedgrain. High scores indicate good grain quality.

KER LB=KERNELS PER POUND. This is the number of kernels per 0.1 pound.

KSZ L=KERNEL SIZE LARGE. Percentage by weight of shelled corn thatpasses through a screen with 25/64 inch diameter openings but does notpass through a screen with 22/64 inch diameter openings.

KSZ MF=KERNEL SIZE MEDIUM FLAT. Percentage by weight of shelled cornthat passes through a screen with 22/64 inch diameter openings and ascreen with 13/64 inch wide slot screen but does not pass through ascreen with 18.5/64 inch diameter openings.

KSZ MR=KERNEL SIZE MEDIUM ROUND. Percentage by weight of shelled cornthat passes through a screen with 22/64 inch diameter openings but doesnot pass through a 13/64 inch wide slot screen or a screen with 18.5/64inch diameter openings.

KSZ S=KERNEL SIZE SMALL. Percentage by weight of shelled corn thatpasses through a screen with 18.5/64 inch diameter openings but does notpass through a screen with 16/64 inch diameter openings.

KSZ TIP=KERNEL SIZE TIPS. Percentage by weight of shelled corn thatpasses through a screen with 16/64 inch diameter openings.

KSZ XL=KERNEL SIZE EXTRA LARGE. Percentage by weight of shelled cornthat does not pass through a screen with 25/64 inch diameter openings.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture ofthe grain at harvest.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant fromthe ground to the tip of the tassel in inches.

POL WT=POLLEN WEIGHT This is the weight of pollen per 100 plants takenon a plot basis. ABS refers to data in absolute, and % MN refers to datapresented as percentage of experimental mean.

PRM=PREDICTED RM. This trait, predicted relative maturity (RM), is basedon the harvest moisture of the grain. The relative maturity rating isbased on a known set of checks and utilizes standard linear regressionanalyses and is referred to as the Minnesota Relative Maturity RatingSystem.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that donot root lodge; plants that lean from the vertical axis at anapproximately 30° angle or greater would be counted as root lodged.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount ofscatter grain (lack of pollination or kernel abortion) on the ear. Thehigher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amountof vegetative growth after emergence at the seedling stage(approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure ofthe hybrid's worth based on information for up to five traits. A cornbreeder may utilize his or her own set of traits for the selectionindex. One of the traits that is almost always included is yield. Theselection index data presented in the tables represent the mean valueaveraged across testing stations.

STA GRN=STAY GREEN. Stay green is the measure of plant health near thetime of black layer formation (physiological maturity). A high scoreindicates better late-season plant health.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plantsper plot.

STK LDG=STALK LODGING. This is the percentage of plants that did notstalk lodge (stalk breakage) as measured by either natural lodging orpushing the stalks and determining the percentage of plants that breakbelow the ear.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure thedegree of blasting (necrosis due to heat stress) of the tassel at timeof flowering. A 1 would indicate a very high level of blasting at timeof flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate therelative size of the tassel. The higher the rating the larger thetassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams)just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate therelative hardness (smoothness of crown) of mature grain. A 1 would bevery soft (extreme dent) while a 9 would be very hard (flinty or verysmooth crown).

TILLER=TILLERS. A count of the number of tillers per plot that couldpossibly shed pollen was taken. Data is given as percentage of tillers:number of tillers per plot divided by number of plants per plot.

TST WT=TEST WEIGHT UNADJUSTED. The measure of the weight of the grain inpounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain inpounds for a given volume (bushel) adjusted for percent moisture.

YLD=YIELD. It is the same as BU ACR ABS.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relativerating for yield based on plot ear piles. The higher the rating thegreater visual yield appearance.

CLN=Corn Lethal Necrosis (MCMV=Maize Chlorotic Mottle Virus andMDMV=Maize Dwarf Mosaic Virus): Visual rating 1-9 score) where a "1" isvery susceptible and a "9" is very resistant.

MDM CPX=Maize Dwarf Mosaic Complex (MDMV=Maize Dwarf Mosaic Virus &MCDV=Maize Chlorotic Dwarf Virus): Visual rating (1-9 score) where a "1"is very susceptible and a "9" is very resistant.

COM SMT=Common Smut (Ustilago maydis): Percentage of plants that did nothave infection.

ANT ROT=Anthracnose Stalk Rot (Colletotrichum graminicola): Visualrating (1-9 score) where a "1" is very susceptible and a "9" is veryresistant.

SLF BLT=Southern Leaf Blight (Bipolaris maydis, Helminthosporiummaydis): Visual rating (1-9 score) where a "1" is very susceptible and a"9" is very resistant.

NLF BLT=Northern Leaf Blight (Exserohilum turcicum, H. turcicum): Visualrating (1-9 score) where a "1" is very susceptible and a "9" is veryresistant.

HC BLT=Helminthosporium Carbonum Leaf Blight (Bipolariszeicola, H.carbonum): Visual rating (1-9 score) where a "1" is very susceptible anda "9" is very resistant.

COM RST=Common Rust (Puccinia sorghi): Visual rating (1-9 score) where a"1" is very susceptible and a "9" is very resistant.

SO RST=Southern Rust (Puccinia polysora): Visual rating (1-9 score)where a "1" is very susceptible and a "9" is very resistant.

EYE SPT=Eyespot (Kabatiella zeae): Visual rating (1-9 score) where a "1"is very susceptible and a "9" is very resistant.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis): Visual rating (1-9score) where a "1" is very susceptible and a "9" is very resistant.

STW WLT=Stewart's Wilt (Erwinia stewartii): Visual rating (1-9 score)where a "1" is very susceptible and a "9" is very resistant.

GOS WLT=Goss's Wilt (Corynebacterium nebraskense): Visual rating (1-9score) where a "1" is very susceptible and a "9" is very resistant.

HD SMT=Head Smut (Spacelotheca reiliana): Percentage of plants that didnot have infection.

DNY MIL=Downy Mildew (Peronosclerosoora sorghi): Percentage of plantsthat did not have infection.

FUS EAR=Fusarium Ear Mold (Fusarium moniliforme): Percentage of plantsthat did not have infection.

EAR MLD=General Ear Mold: Visual rating (1-9 score) where a "1" is verysusceptible and a "9" is very resistant. This is based on overall ratingfor ear mold of mature ears without determining specific mold organism,and may not be predictive for a specific ear mold.

ECB DPE=Dropped ears due to European Corn Borer (Ostrinia nubilalis):Percentage of plants that did not drop ears under second brood cornborer infestation.

ECB 2SC=European Corn Borer Second Brood (Ostrinia nubilalis): Visualrating (1-9 score) of post flowering damage due to infestation byEuropean Corn Borer. A "1" is very susceptible and a "9" is veryresistant.

ECB 1LF=European Corn Borer First Brood (Ostrinia nubilalis): Visualrating (1-9 score) of pre-flowering leaf feeding by European Corn Borer.A "1" is very susceptible and a "9" is very resistant.

ECB 2IT=European Corn Borer Second Brood Tunneling (Ostrinia nubilalis):The average inches of tunneling in the stalk due to second brood(post-flowering) European Corn Borer infestation. Determined bysplitting stalks with a knife, from four internodes above the ear to theground.

DETAILED DESCRIPTION OF THE INVENTION

Inbred Corn Line PHW20 is a white dent corn inbred with superiorcharacteristics and provides an acceptable parental line in crosses forproducing F₁ corn hybrids. This inbred is adapted over most regions ofthe United States. The inbred can be used to produce hybrids fromapproximately 112-124 relative maturity based on the Minnesota RelativeMaturity Rating System for harvest moisture of grain. PHW20 is best usedas a female parent in the production of corn inbreds because it hasadequate yields and a good cold test. However, seed size tends to besmall. The inbred should not be used as a male because of poor pollenshed.

The inbred has shown uniformity and stability within the limits ofenvironmental influence for all the traits as described in the varietydescription information (Table 1) that follows. Most of the data in thevariety description information was collected at Johnston, Iowa. Theinbred has been self-pollinated and ear-rowed a sufficient number ofgenerations with careful attention paid to uniformity of plant type toensure homozygosity and phenotypic stability. The line has beenincreased both by hand and in isolated fields with continued observationfor uniformity. No variant traits have been observed or are expected inPHW20.

Inbred corn line PHW20, being substantially homozygous, can bereproduced by planting seeds of the line, growing the resulting cornplants under self-pollinating or sib-pollinating conditions withadequate isolation, and harvesting the resulting seed, using techniquesfamiliar to the agricultural arts.

                  TABLE 1                                                         ______________________________________                                        PHW20                                                                         VARIETY DESCRIPTION INFORMATION                                               ______________________________________                                        Type: Dent  Region Best Adapated: Most Regions                                A.  Maturity: Zone: Average across maturity zones. Zone 0                         INBRED = PHW20                                                                Heat Unit Shed: 1380                                                          Heat Unit Silk: 1450                                                          No. Reps: 36                                                                   ##STR1##                                                                 B.  Plant Characteristics:                                                        Plant height (to tassel tip): 229 cm                                          Length of top ear internode: 14 cm                                            Number of ears per stalk: single                                              Ear height (to base of top ear): 89 cm                                        Number of tillers: None                                                       Cytoplasm type: Normal                                                    C.  Leaf:                                                                         Color: (B14) Dark Green                                                       Angle from Stalk: 30-60 degrees                                               Marginal Waves: (OH7L) Many                                                   Number of Leaves (mature plants): 19                                          Sheath Pubescence: (WF9) Medium                                               Longitudinal Creases: (OH56A) Few                                             Length (Ear node leaf): 67 cm                                                 Width (widest point, ear node leaf): 8 cm                                 D.  Tassel:                                                                       Number lateral branches: 8                                                    Branch Angle from central spike: 30-40 degrees                                Pollen Shed: Light (WF9) Poor based on production                             experience and was 94% of experiment mean pollen Yield                        Test                                                                          Peduncle Length (top leaf to basal branches): 20 cm                           Anther Color: Greenish Yellow                                                 Glume Color: Green                                                        E.  Ear (Husked Ear Data Except When Stated Otherwise):                           Length: 15 cm                                                                 Weight: 99 gm                                                                 Mid-point Diameter: 41 mm                                                     Silk Color: Yellowish Green                                                   Husk Extension (Harvest stage): Long (8-10 cm Beyond Ear Tip)                 Husk Leaf: 23 cm (Long)                                                       Taper of Ear: Slight Taper                                                    Position of Shank (dry husks): Horizontal                                     Kernel Rows: Distinct, slightly curved, Number = 18                           Husk Color (fresh): Light Green                                               Husk Color (dry): Buff                                                        Shank Length: 11 cm                                                           Shank (No. of internodes): 8                                              F.  Kernel (Dried):                                                               Size (from ear mid-point)                                                     Length: 10 mm                                                                 Width: 8 mm                                                                   Thick: 5 mm                                                                   Shape Grade (% rounds): <20% medium rounds based on                           Parent Test Data                                                              Pericarp Color: Colorless                                                     Aleurone Color: Homozygous-White                                              Endosperm Color: White                                                        Endosperm Type: Normal Starch                                                 Gm Wt/100 Seeds (unsized): 20 gm                                          G.   Cob:                                                                         Diameter at mid-point: 27 mm                                                  Strength: Strong                                                              Color: White                                                              H.  Diseases:                                                                     Corn Lethal Necrosis (MCMV = Maize Chlorotic Mottle Virus                     and MDMV = Maize Dwarf Mosaic Virus): Intermediate                            Anthracnose Stalk Rot (C. Graminicola): Intermediate                          S. Leaf Blight (H. Maydis): Intermediate                                      N. Leaf Blight (H. Turcicum): Susceptible                                     Carbonum Leaf Blight (H. Carbonum): Susceptible                               Eye Spot (K. Zeae): Susceptible                                               Gray Leaf Spot (C. Zeae): Intermediate                                        Stewarts Wilt (E. Stewartii): Resistant                                       Goss's Wilt (C. Nebraskense): Intermediate                                    Common Smut (U. Maydis): Intermediate                                         Head Smut (S. Reiliana): Susceptible                                          Fusarium Ear Mold (F. Moniliforme): Intermediate                          I.  Insects:                                                                      European Corn Borer-1 Leaf Damage (Pre-flowering):                            Intermediate                                                                  European Corn Borer-2 (Post-flowering): Susceptible                       J.  Variety Most Closely Resembling:                                          Character Inbred                                                              Maturity  PHT60                                                               Usage     PHT60                                                               ______________________________________                                         *If maximum is greater than 86 degrees fahrenheit, then 86 is used and if     minimum is less than 50, then 50 is used. Heat units accumulated daily an     can not be less than 0.                                                  

PHT60 is a Pioneer Hi-Bred International, Inc. proprietary inbred (PVPcertificate 8800219)

Items B,C,D,E,F, & G are based on a maximum of 3 reps of data primarilyfrom Johnston, Iowa in 1987 and 1988 plus description information fromthe maintaining station.

                  TABLE 2                                                         ______________________________________                                        ELECTROPHORESIS RESULTS                                                       Isozyme Genotypes for PHW20                                                   Isozyme data was generated for inbred corn line PHW20                         according to the procedure described in Goodman, M. M. and                    Stuber, C. M., "Genetic identification of lines and crosses                   using isoenzyme electrophoresis," Proceedings of the Thirty-                  Fifth Annual Corn and Sorghum Industry Research Conference,                   Chicago, Illinois (1980).                                                     Alleles Present                                                                      Loci  PHW20                                                            ______________________________________                                               ACP1  4                                                                       ADH1  4                                                                       CAT3  N                                                                       DIA1  12                                                                      GOT1  4                                                                       GOT2  4                                                                       GOT3  4                                                                       IDH1  4                                                                       IDH2  6                                                                       MDH1  6                                                                       MDH2  3.5                                                                     MDH3  16                                                                      MDH4  12                                                                      MDH5  12                                                                      MMM   4                                                                       PGM1  9                                                                       PGM2  4                                                                       PGD1  2                                                                       PGD2  5                                                                       PHI1  4                                                                ______________________________________                                    

INDUSTRIAL APPLICABILITY

This invention also is directed to methods for producing a corn plant bycrossing a first parent corn plant with a second parent corn plantwherein the first or second parent corn plant is an inbred corn plantfrom the line PHW20. Further, both first and second parent corn plantscan come from the inbred corn line PHW20. Thus, any such methods usingthe inbred corn line PHW20 are part of this invention: selfing,backcrosses, hybrid production, crosses to populations, and the like.All plants produced using inbred corn line PHW20 as a parent are withinthe scope of this invention. Advantageously, the inbred corn line isused in crosses with other, different, corn inbreds to produce firstgeneration (F₁) corn hybrid seeds and plants with superiorcharacteristics.

As used herein, the terms "plant and plant parts" include plant cells,plant protoplasts, plant cell tissue culture from which corn plants canbe regenerated, plant calli, plant clumps, and plant cells that areintact in plants or parts of plants, such as embryos, pollen, flowers,kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers,silk and the like.

Tissue culture of corn is described in European Patent Application,publication 160,390, incorporated herein by reference. Corn tissueculture procedures are also described in Green and Rhodes, "PlantRegeneration in Tissue Culture of Maize," Maize for Biological Research(Plant Molecular Biology Association, Charlottsville, Va. 1982, at367-372. Thus, another aspect of this invention is to provide cellswhich upon growth and differentiation produce the inbred line PHW20.

The utility of inbred line PHW20 also extends to crosses with otherspecies. Commonly, suitable species will be of the family Graminaceae,and especially of the genera Zea, Tripsacum, Coix, Schlerachne,Polytoca, Chionachne, and Trilobachne, of the tribe Maydeae. Of these,Zea and Tripsacum, are most preferred. Potentially suitable for crosseswith PHW20 may be the various varieties of grain sorghum, Sorghumbicolor (L.) Moench.

Corn is used as human food, livestock feed, and as raw material inindustry. The food uses of corn, in addition to human consumption ofcorn kernels, include both products of dry- and wet-milling industriesand alkaline cooking. The principal products of corn dry milling aregrits, meal and flour. The corn wet-milling industry can provide cornstarch, corn syrups, and dextrose for food use. Alkaline cookingprovides snack foods (i.e., corn chips, tortillas, etc.) Corn oil isrecovered from corn germ, which is a byproduct of both dry- andwet-milling industries.

Corn, including both grain and non-grain portions of the plant, is alsoused extensively as livestock feed, primarily for beef cattle, dairycattle, hogs, and poultry.

Industrial uses of corn are mainly from corn starch from the wet-millingindustry and corn flour from the dry-milling industry. The industrialapplications of corn starch and flour are based on functionalproperties, such as viscosity, film formation, adhesive properties, andability to suspend particles. The corn starch and flour have applicationin the paper and textile industries. Other industrial uses includeapplications in adhesives, building materials, foundry binders, laundrystarches, explosives, oil-well muds, and other mining applications.

Plant parts other than the grain of corn are also used in industry.Stalks and husks are made into paper and wallboard and cobs are used forfuel and to make charcoal.

The seed of inbred corn line PHW20, the plant produced from the inbredseed, the hybrid corn plant produced from the crossing of the inbred,hybrid seed, and various parts of the hybrid corn plant can be utilizedfor human food, livestock feed, and as a raw material in industry.

EXAMPLE Inbred and Hybrid Performance of PHW20

In the examples that follow the traits and characteristics of inbredcorn line PHW20 are given as a line and in hybrid combination. The datacollected on inbred corn line PHW20 is presented for the keycharacteristics and traits.

The results in Table 3 compare PHW20 to PHT60. PHT60 (PVP Certificate#8800219) is an important white endosperm inbred that would be used inthe area in which PHW20 would be used and would cross well with some ofthe same inbred lines. The results show that the two lines differ for anumber of traits. In data collected over four years of research testing,PHW20 proved to be an earlier maturing inbred (flowering and harvestmoisture of the grain), was higher eared and had better cold testresults than PHT60. The lines are quite different for seed size withPHW20 having a higher percentage of small kernels than PHT60 while PHT60has a greater preponderance of large kernels. In the area of disease andinsect resistance, PHW20 has a greater resistance to first broodEuropean Corn Borer than PHT60.

The results in Table 4 compare PHW20 to PHT60 crossed to the same inbredtesters. The results show that the two lines also differ significantlyfor a number of traits in hybrid combination. The PHW20 hybrids showgreater resistance to root lodging, higher grain test weight and highergrain quality score than the PHT60 hybrids. The PHW20 hybrids tend tohave lower ear height, are earlier flowering, and are much drier forharvest moisture of the grain than the PHT60 hybrids. PHW20 has givengood performance in specific combinations.

The results in Table 5 compare a PHW20 hybrid to Pioneer® brand 3283W.Both hybrids have a parent in common other than PHW20. Pioneer® brand3283W is adapted to most of the same areas as the PHW20 hybrid. Theresults show the hybrids differ significantly for a number of traits.Although the PHW20 hybrid yielded 4% less than 3283W it was 1.5 pointsdrier for harvest moisture of the grain, was much earlier to flower, hadhigher test weight and better grain quality. The PHW20 hybrid is ataller hybrid than 3283W. Because of its earlier maturity the PHW20hybrid will perform much better in the more northern white corn growingareas than later maturing white hybrids thus reducing the farmers,freeze risk in the fall. Also, based on samples sent to processors, thePHW20 hybrid has been found to be more acceptable to food cornprocessors because of better milling characteristics than 3283W.

The results in Table 6 compare a PHW20 hybrid to Pioneer® brand 3475.Although the PHW20 hybrid and 3475 have no parents in common, 3475 isgrown in areas where the PHW20 hybrid would be grown and is of similarmaturity. This comparison shows the relative performance between anearly white hybrid and an important yellow dent hybrid of similarmaturity. The results show a number of differences between these twohybrids. The PHW20 hybrid has 0.5 points higher harvest moisture, hasbetter stay green, higher test weight, is taller and has fewer droppedears than 3475. The yield of the PHW20 hybrid is very close (3.2bushels) to 3475 which is very significant for such an early whitehybrid. The inbred PHW20 will make significantly earlier, betterperforming white hybrids than are currently sold.

                                      TABLE 3                                     __________________________________________________________________________    PAIRED INBRED COMPARISON DATA                                                 INBRED #1 - PHW20                                                             INBRED #2 - PHT60                                                             __________________________________________________________________________                BU  BU  BAR BRT EAR EAR EST  CLD CLD  DRP TIL                             VAR ACR ACR PLT STK HT  SZ  CNT  TST TST  EAR LER                     YEAR    #   ABS % MN                                                                              ABS ABS ABS ABS ABS  ABS % MN ABS ABS                     __________________________________________________________________________    TOTAL SUM                                                                             1   51.4                                                                              87  97.0                                                                              100.0                                                                             27.7                                                                               5.9                                                                              26.2 89.7                                                                              104  100.0                                                                              3.6                            2   59.2                                                                              98  94.7                                                                              100.0                                                                             26.0                                                                               5.6                                                                              29.0 85.0                                                                               98  100.0                                                                              1.1                            LOCS                                                                               9   9  19   1  15  14  51   11   11   6  11                              DIFF                                                                               7.8                                                                              11   2.3                                                                               0.0                                                                               1.6                                                                               0.3                                                                               2.8  4.7                                                                               6    0.0                                                                               2.6                            PROB                                                                               .079*                                                                             .090*                                                                             .323    .096*                                                                             .457                                                                              .004#                                                                              .057*                                                                              .062*                                                                             1.00                                                                              .156                   __________________________________________________________________________                GDU  GDU  GRN KER  KSZ KSZ  KSZ KSZ KSZ  KSZ                              VAR SHD  SLK  QUL LB   XL  L    MR  MF  S    TIP                      YEAR    #   ABS  ABS  ABS ABS  ABS ABS  ABS ABS ABS  ABS                      __________________________________________________________________________    TOTAL SUM                                                                             1   142.7                                                                              148.3                                                                              4.9 151.5                                                                              0.0  1.2 19.2                                                                              30.0                                                                              42.4 7.2                              2   147.3                                                                              152.3                                                                              6.9 103.1                                                                              0.6 42.2 26.0                                                                              25.0                                                                               6.0 0.4                              LOCS                                                                               40   37  9    11  5    5    5   5   5   5                                DIFF                                                                               4.5  4.0 2.0  48.4                                                                              0.6 41.0  6.8                                                                               5.0                                                                              36.4 6.8                              PROB                                                                                .000#                                                                              .001#                                                                             .040+                                                                              .006#                                                                             .070*                                                                             .003#                                                                              .385                                                                              .494                                                                              .003#                                                                              .017+                   __________________________________________________________________________                       PLT POL  RT   TAS  TEX TST  SCT SDG                                 VAR  MST  HT  SC   LDG  SZ   EAR WT   GRN VGR                        YEAR     #    ABS  ABS ABS  ABS  ABS  ABS ABS  ABS ABS                        __________________________________________________________________________    TOTAL SUM                                                                              1    16.6 78.9                                                                               4.3 97.4  5.4 5.8 57.0  6.7                                                                               3.5                                2    19.9 80.8                                                                               5.5 93.1  4.6 7.8 60.2  6.9                                                                               5.8                                LOCS   9  16  20    2   20   8    9   18  19                                  DIFF  3.3  1.8                                                                               1.2  4.3  0.9 2.0  3.3  0.2                                                                               2.3                                PROB  .000#                                                                              .033+                                                                             .009#                                                                              .136                                                                               .000#                                                                              .007#                                                                             .002#                                                                              .586                                                                              .000#                     __________________________________________________________________________                     STA  STK  STK YLD COM EAR ECB  ECB                                                                              NLF                                                                              STW                                  VAR GRN  CNT  LDG SC  SMT MLD 1LF  2SC                                                                              BLT                                                                              WLT                     YEAR         #   ABS  ABS  ABS ABS ABS ABS ABS  ABS                                                                              ABS                                                                              ABS                     __________________________________________________________________________    TOTAL SUM    1    2.8 26.1 85.0                                                                               6.0                                                                              0.0  7.2                                                                               5.5 3.0                                                                              4.0                                                                              9.0                                  2    7.1 26.9 95.5                                                                               5.4                                                                              0.0  7.5                                                                               4.4 3.5                                                                              5.0                                                                              8.0                                  LOCS                                                                              15   45    8  21  1   17  11   2  2  1                                    DIFF                                                                               4.3  0.8 10.5                                                                               0.6                                                                              0.0  0.3                                                                               1.2 0.5                                                                              1.0                                                                              1.0                                  PROB                                                                               .000#                                                                              .040+                                                                              .076*                                                                             .208    .396                                                                              .011+                                                                              .500                                                                             .500                      __________________________________________________________________________     *=  10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 4                                     __________________________________________________________________________    Average Inbred by Tester Performance Comparing PHW20 to PHT60 crossed to      the same                                                                      Inbred Testers and Grown in the Same Experiments. All Values are              Expressed as percent                                                          of the experiment mean except Predicted RM, Selection Index, and Yield        (Bu./Ac.).                                                                    __________________________________________________________________________                     SEL                                                                              BU       GDU STK RT  BAR                                                                              STA                                      Inbred                                                                              PRM IND                                                                              ACR                                                                              YLD                                                                              MST                                                                              SHD LDG LDG PLT                                                                              GRN                               __________________________________________________________________________    TOTAL  REPLIC.                                                                              38  38                                                                               38                                                                              38 38  9   32  16  4  21                               MEAN WTS                                                                             PHW20 115  99                                                                              105                                                                              94 86 94  100 104 115                                                                               55                               MEAN WTS                                                                             PHT60 121 101                                                                              108                                                                              96 97 98  107  73  97                                                                              120                                      DIFF.  6   3  3  2 11  4   7   30  18                                                                               65                               __________________________________________________________________________                      TST COB                                                                              GRN SDG EST                                                                              PLT                                                                              EAR                                                                              DRP                                                                              BRT                                          Inbred                                                                              WTA SC QUL VGR CNT                                                                              HT HT EAR                                                                              STK                              __________________________________________________________________________    TOTAL       REPLIC.                                                                              38    34  12   31                                                                               31                                                                               16                                                                               16                                 MEAN WTS    PHW20 101    95  95  100                                                                              100                                                                               98                                                                              100                                 MEAN WTS    PHT60 100    95  99   99                                                                              100                                                                              101                                                                              100                                             DIFF.  0      6   0   1  0  3  0                                  __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    #1- PHW20 HYBRID                                                              #2 - PIONEER ® BRAND 3283W                                                __________________________________________________________________________                                 BU   BU        GDU  STK  RT  STA                               VAR       SEL  ACR  ACR  MST  SHD  LDG  LDG GRN                 YEAR    REGION                                                                              #    PRM  IND  ABS  % MN ABS  ABS  ABS  ABS ABS                 __________________________________________________________________________    TOTAL SUM     1    116  95   131.7                                                                              95   19.2 137.0                                                                              89.0 81.0                                                                               3.5                              2    121  99   137.3                                                                              99   20.8 142.2                                                                              91.0 78.4                                                                               4.8                              LOCS  18  17    80  80   82    19  74   26  40                                DIFF  5    3    5.6  4    1.5  5.2  2.0  2.6                                                                               1.4                              PROB   .000#                                                                             .047+                                                                               .000#                                                                             .001#                                                                              .000#                                                                               .000#                                                                             .126                                                                               .349                                                                              .000#              __________________________________________________________________________                                TST  GRN EST STK PLT  EAR  DRP BRT                                        VAR WTA  QUL CNT CMT HT   HT   EAR STK                          YEAR    REGION                                                                              #   ABS  ABS ABS ABS ABS  ABS  ABS ABS                __________________________________________________________________________              TOTAL SUM     1   57.5  6.5                                                                              54.3                                                                              45.7                                                                              89.6 42.3 99.7                                                                              95.7                                       2   57.2  6.2                                                                              55.2                                                                              46.2                                                                              84.0 37.8 99.6                                                                              99.1                                       LOCS                                                                              80   76  51  87  41   41   38   3                                         DIFF                                                                               0.3  0.3                                                                               1.0                                                                               0.5                                                                               5.7  4.4  0.0                                                                               3.4                                       PROB                                                                               .003#                                                                              .054*                                                                             .053*                                                                             .072*                                                                             .000#                                                                              .000#                                                                              .800                                                                              .327              __________________________________________________________________________     *=  10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

                                      TABLE 6                                     __________________________________________________________________________    #1- PHW20 HYBRID                                                              #2 - PIONEER ® BRAND 3475                                                 __________________________________________________________________________                           BU  BU       GDU STK RT   BAR STA  TST                            VAR     SEL ACR ACR MST  SHD LDG LDG  PLT GRN  WTA                 YEAR REGION                                                                              #   PRM IND ABS % MN                                                                              ABS  ABS ABS ABS  ABS ABS  ABS                 __________________________________________________________________________    TOTAL      1   114 91  117.2                                                                              93  20.1                                                                              136.1                                                                              91.9                                                                             86.7 94.8                                                                               4.5  57.7               SUM        2   114 95  118.8                                                                              94  19.7                                                                              136.3                                                                              91.9                                                                             91.4 95.6                                                                               3.9  57.6                          LOCS                                                                               35 34  169 169 172   46 156 32   35  106  169                            DIFF                                                                               1   3   1.6                                                                               1   0.3  0.2                                                                               0.0                                                                               4.8  0.7                                                                               0.7  0.2                           PROB                                                                                .162                                                                             .072*                                                                              .284                                                                              .458                                                                              .011+                                                                              .659                                                                              .974                                                                             .030+                                                                              .327                                                                               .000#                                                                              .046+             __________________________________________________________________________                          COB  GRN SDG  EST STK PLT  EAR  DRP  BRT                                  VAR SC   QUL VGR  CNT CNT HT   HT   EAR  STK                       YEAR REGION                                                                              #   ABS  ABS ABS  ABS ABS ABS  ABS  ABS  ABS                __________________________________________________________________________           TOTAL      1    5.9  6.6                                                                               4.4  56.2                                                                              44.1                                                                             92.2 40.9  99.8                                                                              97.8                      SUM        2    7.4  6.4                                                                               5.9  56.2                                                                              44.5                                                                             85.2 37.6  99.3                                                                              99.4                                 LOCS                                                                              12   152 80   130 194 86   86   109   7                                   DIFF                                                                               1.5  0.1                                                                               1.4  0.1                                                                               0.4                                                                               7.0  3.3  0.5  1.5                                 PROB                                                                               .007#                                                                               .306                                                                             .000#                                                                               .947                                                                              .253                                                                             .000#                                                                              .000#                                                                               .000#                                                                             .218              __________________________________________________________________________     *=  10% SIG                                                                   + = 5% SIG                                                                    # = 1% SIG                                                               

Deposits

Applicant has made available to the public without restriction a depositof at least 2500 seeds of inbred PHW20 with the American Type CultureCollection (ATCC), Rockville, Md. 20852 USA, ATCC Deposit No. 75074. Theseeds deposited with the ATCC are taken from the same deposit maintainedby Pioneer Hi-Bred International Inc., 700 Capital Square, 400 LocustStreet, Des Moines, Iowa 50309 since prior to the filing date of thisapplication. The deposit will be maintained in the ATCC depository,which is a public depository, for a period of 30 years, or 5 years afterthe most recent request, or for the effective life of the patent,whichever is longer, and will be replaced if it becomes nonviable duringthat period.

What is claimed is:
 1. Inbred corn seed designated PHW20 having ATCC accession No.
 2. A corn plant produced by the seed of claim
 1. 3. Tissue culture of the plant of claim
 2. 4. Tissue culture according to claim 3 comprising regenerable cells of a plant part selected from meristematic tissue, anthers, leaves, embryos, protoplasts, and pollen.
 5. A corn plant regenerated from the regenerable cells of a tissue culture according to claim
 4. 6. An inbred corn plant having all the physiological and morphological characteristics of the seed of claim
 1. 7. A method to produce a novel hybrid corn seed comprising the steps of:(a) planting in pollinating corn inbred lines PHW20 or cross involving PHW20 and another inbred line or cross; (b) cultivating corn plants resulting from said planting until the time the plants bear flowers; (c) emasculating the flowers of the plants of either inbred line or cross; (d) allowing natural cross pollinating to occur between said inbred lines, crosses or inbred and cross; and (e) harvesting seeds produced on said emasculated plants of the inbred line or cross.
 8. An F₁ hybrid corn plant and seed thereof produced by crossing an inbred corn plant according to claim 2 with another, different corn plant. 